Method of driving rock excavations



Flwll cw. ZHSWEMEEF? 1 SEARCH ROOM July 28, 1959 E. 1. JANELID ET'AL 2,896,929 METHOD OF DRIVING ROCK EXCAVATIONSY ,2 Filed Sept. 8, 1958 3 shegtssheet 1 July 28, 1959 E. l. JANELID ET AL 2,396,929

METHOD OF DRIVING ROCK EXCAVATIONS Filed Sept. 8, 1958 s Sheets-Sheet 2 E. JA NELIID ETAL 2,896,929

I Mame]: 0F DRIVING ROCK EXCAVATIONS July: 28, 1959 3 Sheets-Sheet 3 Filed Sept 8. 1958 United States Patent METHOD OF DRIVING ROCK EXCAVATIONS Erik I. Janelid, Djursholm, and Karl G. Olsson, Tumba, Sweden Application September 8, 1958, Serial No. 759,648

Claims priority, application Sweden February 25, 1958 6 Claims. (Cl. 262-1) This invention relates generally to underground excavating or mining and more particularly to a novel method of stoping and driving an excavation or mine working in a given direction.

In known systems of underground excavating or mining the usual procedure in driving an excavation in a particular direction, as for example drifts, stopes etc., is carried out by drilling holes, subsequently charged with explosives, in the face or breast of the mine working from which material is to be removed. The holes are drilled into the breast substantially parallel to the direction in which the excavation is to be driven or advanced and some of the holes may be drilled oblique thereto so that the material being mined breaks loose on the breast usually in the shape of a wedge depending on the manner in which the holes are drilled and charged with explosives. These known systems have many attendant disadvantages in that miners or working crews that are to remove the material from the excavation or mine working are not able to continue to work the excavation while the drilling and blasting operations are taking place since these operations take place on the face of the mine working or excavation from which the material is to be removed. Consequently there is a loss of time as to the removal of material and a particular excavation cannot be driven continuously thereby decreasing the speed of excavating and increasing the cost per ton of material removed.

It is a principal object of the present invention to provide a method, usable in various systems of underground excavating or mining, for driving an excavation wherein the drilled holes can be located parallel with the face of the mine working or excavation from which the material is to be removed.

It is another main object of the invention to provide a method for driving an excavation wherein the preparatory drilling operation for subsequent blasting can take place from a separate space while a particular excavation or working is having the material, for example, rock, ore or mineral, removed therefrom greatly increasing the efliciency of the entire excavating or mining operation.

Another object is to provide a safe method whereby the miners are well protected during the charging and blasting operation since in each instance the blasting takes place in a compartment or room separate from the room or space from which drilling and control of the explosion or blasts takes place.

Still another object is to provide a method for driving an excavation wherein for a given amount of rock fewer holes for blasting need be drilled in a simpler hole pattern than in known methods, for breaking loose the material from a face of a mine working or stope.

Another object is to provide a method for driving an excavation where the explosion forces being sufliciently employed to greatly reduce, over the known methods, the charge of explosive expended.

Patented July 28, 1959 Still another object is to provide a method for driving an excavation, where fewer types of standard charges need be used.

A feature of the method in accordance with the invention is that drilling and blasting is carried out from an existing space, as for example, from outside a rock formation or from a drift, tunnel, cross-cut, or raise and the like e.g. driven in known manner. A plurality of spaced holes are drilled into a face. of the existing space, as for example, the side wall of the space. The holes are drilled transversely to the longitudinal direction of the new excavation and substantially parallel with the working face of said excavation.

The expression working face is in the following used for indicating the face of the excavation from which the material is to be removed. This face need not be a plane surface but may be curved in any suitable manner.

At least some of the holes are drilled to a depth greater than the combined transverse dimension of the excavation to be driven and the transverse dimension of a wall portion or pillar of material that is to remain between the excavation to be driven and the existing space. The holes are spaced lengthwise on the side wall and arranged in rows or in a selected pattern for obtaining the best blasting efficiency and controllably shaping the profile of the excavation to be driven. The drilled holes are not charged with explosives their full length but are individually charged only along one or more selected portions or lengths thereof lying in front of the desired section of the excavation or mining working in the driving direction.

Moreover the charged portions or lengths of the drilled holes are spaced laterally from the side wall of the existing space so that when the explosive charges are detonated or otherwise exploded the material to be removed is broken loose along a face or breast of an excavation which will be laterally spaced from the existing space and a wall or pillar of material will remtain between the existing space and the excavation being driven in a direction substantially parallel to the existing space. This remaining wall can be subsequently removed by charging and blasting the holes which were originally drilled therein.

The roof of the excavation to be formed can be reinforced prior to beginning of the blasting so that upon completion of the blasting the removal of the ore or other material from the excavation can begin substantially immediately thereafter under safe conditions. To this end some of the holes drilled from the side wall of the existing space are located so that these holes adapted to receive reinforcement rods will lie outside the wall-faces, for example above the roof of the excavation to be formed. Reinforcing rods are disposed in these holes prior to llilaisting the material loose with the charges in the other Other objects, features and advantages of the invention will be understood from the following description and claims in conjunction with the accompanying drawings which illustrate by way of example preferred embodiments of the method, and in which Fig. 1 is a cross-section view taken along line I---I in Fig. 3 of horizontally extending excavations to be driven parallel to an existing passageway in accordance with the invention;

Fig. 2 is a longitudinal sectional view taken along line II11 in Fig. 1 and is illustrative of the manner in which the holes are drilled and arranged according to the invention;

Fig. 3 is a plan view of the excavation of Fig. 1;

Fig. 4 is a vertical longitudinal sectional view illustrating the method of driving the stopes upwardly from a haulage level by drilling from an adjacent raise or winze;

Fig. is a cross section view taken along line V-V in Fig. 6 of an existing drift or stope and the excavation to be driven and is illustrative of the method of reinforcing the roof of the excavation to be driven according to the invention;

Fig. 6 is a plan view in a section taken along line VI-VI in Fig. 5;

Fig. 7 is a plan view similar to that in Fig. 3 illustrating a modified manner in which the holes are drilled and arranged according to the invention;

Fig. 8 is a plan view similar to that in Fig. 7 illustrating a manner in which the holes are drilled from two existing spaces located on both sides of an excavation to be driven;

Fig. 9 is a vertical longitudinal sectional view illustrating the manner in which the holes are drilled from outside a rock formation and;

Fig. is a vertical cross sectional view taken along line XX in Fig. 9 illustrating a modified manner of arranging reinforcement holes to be drilled.

While the method of driving an excavation according to the present invention will be described with respect to underground mining of an ore or mineral body it will be understood that the method is applicable to the excavation of tunnels for highways, railways and the like. Moreover, while the method of the invention will be described as applied to two stoping systems it will be understood the method may be employed with various systems such as underhand stoping, sub-level caving, room and pillar mining, etc. and with deposits horizontal or having a dip or being substantially vertical.

In the drawings (Figs. 1-3) an existing space or passageway 1 such as a drift is excavated in known manner. A plurality of holes 3 are drilled into a face other than the end face of the drift which itself must be worked and advanced, as for example, in side wall 2 of the drift and are drilled transversely to the excavation to be driven The holes 3 are drilled to a predetermined depth depending upon the width of the excavation and the number of excavations that are to be driven from the existing space. Thus at least some of the holes extend across the entire region to be worked. By way of example in Figs. 1 and 3 the method is described as applied to the room and pillar" method of mining as employed for systematically cutting a thin deposit, that is horizontal or dips at a small angle with the horizontal. In the example two parallel drifts 4 and 5 are to be driven parallel to drift 1 with intermediate continuous pillars 4' and 5' being allowed to remain to support the overburden or roof. If desired these pillars may later be removed as hereinafter described.

The holes 3 are drilled in a selected spaced relationship in the side wall 2 and in a direction substantially parallel to the working face of the excavation to be driven. The holes are arranged in rows or in a pattern as shown in Fig. 2 for controllably determining the shape of the excavation or drift to be driven. At least some of the holes are drilled to a depth exceeding the transverse dimensions of the two drifts 4 and 5 that are to be excavated and drilled transversely of the intermediate pillars. These holes are not charged with explosives throughout the full length thereof. Only certain portions 6, 6, 7 and 7' (shown with a center line) of each hole 3 are charged with explosives. The portion or lengths that are charged are spaced laterally from the side wall 2 and spaced axially from each other as shown. The charged portions are aligned in a direction corresponding to the direction in which the new excavations or drifts are to be driven. The length of the individual charged portions corresponds substantially to the transverse dimensions of the excavations that are to be blasted. The upper charged portions 6' and 7 may be of lesser length than the lower charged portions or 4 lengths so that upon blasting the drift will have the sectional configuration shown.

The charges are set off so that slices of material are initially broken loose on a face of a drift 10 and subsequently removed forming the stopes 4, 5 as shown in Fig. 3, substantially parallel to the existing space or drift 1. The charges set off to progressively advance the breasts of the workings or drifts 4 and 5 in a direction corresponding to the wanted lengthwise direction of the drifts 4 and 5. It can readily be seen that the explosion forces will seek the path of least resistance, in a direction toward the breast of the individual stopes or drifts 4 and 5, so that reduced charges can be effectively employed greatly reducing the cost of the explosives as against the known methods of drifting and tunneling.

It will be understood that the breast or face 11 of the drift 1 is advanced by the known method of drilling the holes 11 substantially parallel to the general lengthwise direction of the drift 1 and obliquely thereto, as shown, with the blasting being done in the usual manner.

By employing the present invention the drilling can take place from the existing drift or space without interfering with the removal of loose and broken material in stopes 4 and 5 subsequent to the blasting. The miners are well protected during the blasting since drift 1 from which the charges are set oif provides a separate compartment from stopes 4 and 5 which are also well separated from each other by intermediate pillars.

The pillars 4' and 5' may in certain cases, as for example in sub-level caving be removed by charging and blasting the holes 3 therein. Accordingly it can be seen in such cases that all drilled holes can be effectively used. The space or drift 5, as the breast thereof is advanced, can eventually be employed for drilling therefrom as heretofore discussed with respect to the drilling in space 1 so that other excavations (not shown) can be driven from space 5.

In some cases it is preferable to keep the excavations such as drifts or stopes 4 and 5 as wide as possible, but the width depends upon the characteristics of the ore deposit or rock formation, being mined or excavated. For this purpose the present invention provides a method, hereinafter described, of reinforcing the roof or side walls of the excavations to be blasted. Maintaining the excavations wide will give better efiiciency by blasting and makes it possible to employ bigger mechanized equipment for loading and removing the material broken loose by the blasting.

In the event that a second horizon or level is to be driven from the existing space such as drift 1 the same principles heretofore described may be employed. The holes 3 may be drilled as before into a face extending lengthwise of space 1, in this instance the floor of drift 1, as shown in Fig. l, to drive an excavation or drift 12 in a manner similar to the driving of drifts 4 and 5.

The method of the present invention may be employed, for example, in conjunction with the system of overhand stoping wherein the stope 13 is advanced upward as shown in Fig. 4. It being understood that for convenience and to maintain uniformity in the drawing the holes drilled for blasting are numbered the same in Figs. l5. The holes 3 are drilled from a raise or winzes 14 extending between levels 15 and 15' parallel to the working face 13' of the stope 13 to be driven and the charged portions 16 are aligned vertically in the direction in which the stope 13 is to be advanced upwardly. Moreover the charged lengths of the holes 3 are spaced from wall 14' so that upon blasting the protective and support pillar 17 remains intact to support the back of material between levels. The shots are fired so that the ore, rock or material is broken loose in slices upwardly from below.

By employing the method of the present invention the stope 13 is advanced progressively upward with the broken material being hauled away at level 15. The method eliminates the need for access by the miners to the stope breast so that the need of platforms, ladders or the like is eliminated. Furthermore the need for expensive timbering or roof bolting is less by the use of the present invention.

It is to be noted that the holes may be drilled in suitable inclination relative to the direction of advancement of the excavation or mine working to be driven and may form an arbitrary angle with the wall of the existing space. Neither need the holes be parallel and Fig. 7 illustrates an embodiment of the invention where two groups of parallel holes 23 and 24 respectively form an angle with each other which arrangement of the holes permits a greater burden, which results in less explosive per cf. of broken rock. Moreover smoother side-walls are obtained. In this case the working face of the excavation will be curved or substantially V-shaped. The groups of holes 23, 24 drilled from one and the same existing space are of diiferent lengths so that the holes of group 23 are drilled approximately to the middle line of the excavation to be driven and the holes of group 24 extends approximately over the whole width of said new excavation. The first mentioned holes are charged at 25 along its portion lying in front of the working face of the new excavation and the holes 24 are charged along a portion 26 beginning approximately at the middle line of said new excavation to the side thereof opposite to said existing space 1.

Moreover the holes may be drilled from existing spaces opposite the excavation to be driven as shown in Fig. 8, where groups of parallel holes 27 and 28 are drilled from two oppositely located spaces 1 and 1. Each group of holes '27, 28 is charged along selected portions 29, 30 as shown in the figure to extend substantially over the whole area of the working face to be blasted.

As mentioned above the existing space may be the surface 31 of a rock formation in which the excavation 4 is to be driven. Holes 32, parts 33 thereof being adapted to be charged and blasted in the manner and for the purpose described above, are for example drilled vertically into the rock.

As stated heretofore the method according to the invention makes provision for reinforcing the roof of the excavation to be driven prior to blasting so that the broken material in the excavation can be immediately attacked and the stope advanced. To this end holes 18 are drilled (Fig. at an angle with the roof of the existing space, as for example, a drift 19 and extend transversely across the entire region to be worked in similar manner as the holes 3. These holes -18 lie above the roof of the excavation 20 which is to be driven alongside drift or space 19. The holes 18 are preferably drilled at the time holes 3 are drilled. Reinforcing rods 21 are disposed longitudinally in these holes and may be anchored in place or otherwise cemented therein. The rods 21 extend preferably the full width of the excavation 20 so that the ends thereof rest on or can be fastened in solid portions of material such as intermediate pillars. These rods may also be removably disposed in the holes 18 and may be provided with a hook as shown with respect to rod 21 so that they can be later removed or recovered by withdrawing them into drift 19. It being understood that the rods may be constructed, for example, as connectable sections if a very wide region is to be worked at one time.

With respect to the system shown and described in Fig. 4, the reinforcement holes (not shown) may be drilled in the face 14' at an angle with respect to the projected profile of the excavation or stope 13 so that the sides thereof are reinforced.

With respect to the system shown and described in Fig. 9 the reinforcement holes 34 illustrated in the cross sectional view in Fig. are drilled vertically. Thereby the roof and side walls of the excavation 4 may be suitably secured before blasting by inserting reinforcing rods 35 thereinin the same manner and for the same purpose as described in connection with Figs. 5 and 6. It is to be noted that the parts of the blasting holes not charged extending from the roof of the excavation to be blasted and the face of the drilling space may be used for reinforcements.

In the event that conditions render it necessary additional reinforcement can be provided by use of ordinary roof bolts 22 as the stope 20 is advanced and the broken material is removed therefrom. Accordingly, it is possible to eliminate the expensive timbering methods currently employed in supporting the roof or overburden.

A safety feature resulting from the present invention is that excavations driven by the method of the present invention can be effectively ventilated by blowing air into the excavation under pressure through the drilled holes or specially made openings by means (not shown) from an existing space such as drifts 1 and 19.

It is readily apparent that the method according to the invention greatly increases the efficiency of the mining operation and reduces costs. There is a savings, over known methods, as to costs for blasting since fewer holes need be drilled and the full force of the explosive force is employed reducing the quantity of explosives required per unit volume of broken material. If the thickness of the pillars is limited with respect to the transverse dimensions of the excavations driven the volume of broken material per unit length of the total length of the holes drilled will be greater than in known methods.

By using the method disclosed herein it is possible to effect optimum use of poweredloading equipment since this equipment will not be idle during the drilling as in the case in the known methods. Moreover since blasting can be carried on in a series of shots, to slice the material in a plurality of successive slices on the breast of the excavation being advanced or driven, it can be seen that more broken material will be available than in the case where the drilling and blasting takes place on the face that is to be advanced.

Drilling equipment is also employed almost continuously since drilling can take place while the blasting and removal operations are taking place. This makes it also possible and advantageous to use large drilling equipments of high efliciency which, of course, greatly reduces the costs of drilling.

The pattern in which the holes 3 are drilled can, of course, be varied to suit the need of the situation taking into consideration such variables as stratification etc. Once drilled those parts of the holes that are not charged and blasted remain in the material so that if it is desired to remove pillars etc. subsequent to stoping the pillar holes can be charged and the pillars blasted as stated heretofore. While the walls of the excavation driven by the method herein disclosed may not always be substantially smooth, because of the differences in strata etc., this can be rectified afterwards by smooth-blasting in known manner.

It can be seen that in vertical or steeply inclined excavations the stopes can be advanced completely under control from an existing space without need of access to the breast of such a stope for advancing it. The broken material in such situations is easily removed from the bottom of the excavation.

While the method according to the invention has been illustrated and described with respect to some underground systems of mining and more particularly underground stoping systems it will be understood that the invention is in no way limited to these systems and many changes and applications may be made within the spirit and scope of the invention as defined by the following claims.

Trial mining of horizontal drifts having a section of 20 x 12 feet has been carried out in alun slate by aid of the method according to the invention. A volume of 10 cu. ft. firm rock was broken by aid of 1.0 feet drilled hole and 0.27 lb. explosive. Corresponding figures for 7 an ordinary driving method with wedge out were 1.2 feet drilled hole and 0.33 lb. explosive. The width of the intermediate pillar was 10 feet.

At driving a drift having a section of 8.3 x 7.3 feet in compact magnetite by aid of the method according to the invention 10 cu. ft. firm rock were broken by aid of 5.0 feet drilled hole and 1.0 lb. explosive. Corresponding figures for an ordinary driving method with wedge out were 5.4 feet drilled hole and 1.4 lb. explosive. The width of the intermediate pillar was 8.3 feet.

We claim:

1. A method for driving an excavation separated from and substantially parallel with an existing working space of arbitrary inclination, which comprises, drilling holes into a selected face of said space, in a direction substantially parallel with and at a predetermined distance in front of the end face to be advanced by the excavation to be driven and transversely to the lengthwise direction of said new excavation, the holes being drilled to a predetermined depth which is greater than the combined transverse dimensions of said excavation to be driven and the wall portion that is to remain between said excavation and said existing Working space; charging with explosives the individual holes along at least one portion thereof spaced from said face of the existing working space a predetermined distance corresponding to the transverse dimension of the wall portion that is to remain between said existing space and said new excavation, the length of the individual charged portions being selected in response to the transverse dimension of the excavation to be driven, so as to break loose the material along said end face of the excavation to be driven, when causing the explosive charges in said holes to explode in a predetermined sequence and clearing away broken material resulting from the explosion of the charges.

2. A method for driving an excavation separated from and substantially parallel with an existing working space of arbitrary inclination, which comprises,'drilling holes into a selected face of said space, in a direction trans-' versely to the lengthwise direction of the excavation to be driven, the holes being drilled in groups, the holes of each group being substantially parallel with each other and the working face at predetermined distances from said face, said groups of holes forming an angle with each other, at least one of said groups being drilled to a predetermined depth which is greater than the combined transverse dimension of the excavation to be driven and the wall portion that is to remain between said excavation and said existing working space; charging with explosives the individual holes along at least one portion thereof spaced from said face of the existing space a predetermined distance, the individual charged portions of associated holes of said groups being selected to correspond substantially with the transverse dimension of the excavation to be driven; causing the explosive charges in said holes to explode to break loose the material along the end face of the excavation to be driven so as to form an angle shaped end face of said excavation substantially parallel with the blasted portions of said groups of holes and clearing away broken material resulting from the explosion of the charges.

3. A method for driving rock excavation from outside a rock formation, which comprises, drilling holes into a selected area of the rock face in a direction substantially parallel with and at a predetermined distance in front of the end face to be advanced of the excavation to be driven and transversely to the lengthwise direction of said excavation, at least some of the holes being drilled to a predetermined depth which is greater than the combined transverse dimensions of the excavation to be driven and the portion of the rock that is to remain between said excavation and the rock face; charging with explosives the individual holes along at least one portion thereof spaced from said rock face a predetermined distance, the individual charged portions being selected to correspond substantially with the transverse dimension of the excavation to be driven; causing the explosive charges in said holes to explode in a predetermined order to break loose the material along said end face of the excavation to be driven, and clearing away broken material resulting from the explosion of the charges.

4. A method for driving an excavation separated from an existing working space such as a rock face, a drift, cross-cut, tunnel, shaft, raise or stope and the like, which comprises, drilling holes into a selected face of said space, in a direction substantially parallel with and at a predetermined distance in front of the end face to be advanced of the excavation to be driven and transversely to the lengthwise direction of said excavation, at least some of the holes being drilled to a predetermined depth which is greater than the combined transverse dimension of the excavation to be driven and the wall portion that is to remain between the excavation and said existing working space; charging with explosives the individual holes along at least one portion thereof spaced from said face of the existing working space a predetermined distance, the individual charged portions being selected to correspond substantially with the transverse dimension of the excavation to be driven; causing the explosive charges in said holes to explode to break loose the material along said end face of the excavation to be driven, charging at least a portion of the holes in the remaining portion of material, causing said charges in the remaining material to explode in a predetermined order to break loose the material between said excavation and the working space, and removing the broken material.

5. A method for driving an excavation separated from and substantially parallel with an existing working space such as a rock face, a drift, crosscut, tunnel, shaft, raise or stope and the like which comprises, drilling holes into a selected face of said space, in a direction transversely to the lengthwise direction of said excavation, at least some of the holes being drilled to a predetermined depth first mentioned holes only along at least one portion thereof spaced from said face of the existing space a predetermined distance; the individual charged portions being selected to correspond substantially with the transverse dimension of the excavation to be driven; causing the explosive charges in said holes to explode to break loose the material along the end face of the exca ation to be driven, and clearing away broken material resulting from the explosion of the charges.

6. A method for driving a continuous rock excavation separate from a drilling space comprising the steps of drilling in an available rock face spaced holes transversing the projected area of said excavation; successively charging said holes with explosives along selected portions thereof corresponding to said projected area and spaced from said available face; causing the explosive charges to explode to break loose the material over said projected area leaving a wall portion between the excavation and the drilling space and clearing away the broken material from the excavation through the blasted portion of the 31? No references cited. 

